Method and apparatus for coating an insulated conductor



March 29, 1960 c. w. ABBOTT METHOD AND APPARATUS FOR COATING AN INSULATED CONDUCTOR 6, 1957 3 Sheets-Sheet 1 Filed, Feb.

' INVENTOR (240F155 I74 flzearr TMHHM E N March 29, 1960 w. ABBOTT2,930,713

METHOD AND APPARATUS FOR comm:- AN INSULATED CONDUCTOR Filed Feb. 6,1957 5 Sheets-Sheet 2 INVENTO (244,945: 14 )35607'7' March 29; 1960 c,w, ABBOTT 2,930,718

METHOD AND APPARATUS FOR COATING AN INSULATED CONDUCTOR I Filed Feb. 6,1957 s Sheets-Sheet s 1 .E. T q 4 i j d ai //4 f INVENIIOR (399,915: 1/4515077- METHOD AND APPARATUS FOR COATING AN INSULATED CONDUCTOR CharlesW. Abbott, Clearwater Beach, Fla., assignor to The Whitney BlakeCompany, New Haven, Conn, a corporation of Connecticut ApplicationFebruary 6, 1957, Serial No. 638,507

6 Claims. (Cl. 117-218) vThis invention relates to a process of coatingand particularly color coating previously formed insulated conductorsand the like and to the resulting product, and to apparatus for carryingout various steps of the process and to a system of apparatus and acombination of apparatus elements for carrying out the series of stepscomprising the process.

While it has broader application, the process is particularly adaptedfor coating telephone cords-which are colored to match colored telephonesets and used to interconnect the receiver or receiver-mouthpiececombination with the main body of the telephone set and to intercon-Cords or" nect the set with the circuit connecting means. this typeusually comprise three or four conductors, each comprising a conductivecore of several small gauge tinsel wires twisted together containedwithin an outer jacket of neoprene, the periphery of which is not truly.circular. Telephone cord is often made retractile by forming it, or partof it, into a coil of spiral turns of the cord to insure its flexibilityand to cause it to retract and be out of the way when not extended bythe user. The insulation on the retractile cords is only partlyvulcanized at the time the insulation is extruded on the cord, andvulcanization is completed after the coil portion of the cord has beengivena set to cause it to retract to a coiled form after being extended.

It is especially contemplated to apply the coating process disclosedherein to insulated conductors which have been previously jacketed withrubber, neoprene or the like.

Coating may be applied for any of a variety of reasons, for example, forincreasing the wear resistance of the insulation, or to give it adesired color, or for both reasons.

The term rubber is used herein broadly, to include rubber substitutes,such as neoprene and similar insulating materials.

The term jacketed conductor is used herein broadly to include a singleinsulated core or a plurality of such insulated cores enclosed in ajacket, and the term insulation is used herein broadly to include asingle covering or a plural number of coverings, such for example asoccur when a plurality of individually insulated cores are enclosed in acommon jacket.

It is well-known that a conductor insulated with rubber and protectedwith a covering or coating adapted to resist abrasion has certainadvantages over a conductor insulated with plastic. Plastic insulation,even when made according to standards approved by the Fire UnderwritersLaboratories, is not truly satisfactory, for code wire and common formsof cords because of its cold flow qualities and lack of dependableelasticity. It is particularly unsatisfactory for cords which are to becoiled to make them retractile as their insulation needs to beparticularly resilient and resistant to wear. However, plastic whichcame into use during World War II, due

'to the shortage of rubber, has largely replaced rubber as insulationfor code wire and common forms of cords due to thecost ditferentialbetween the single step operation 2,930,718 Patented Mar. 29, 196 0 icetive colors having permanent, non-staining characteristics,

due largely to the ditficulties of coating cords of non-cir cular crosssection. cords it has been, and still is, the practice to coat theinsulated conductors by hand-dipping them in what is a time consuming,cumbersome operation. I

It has been suggested, in my Patent No. 2,175,099 to extrude a viscousrubber insulation onto-a conductor, vulcanize the insulation, andextrude a viscous, solvent containing wear resistant coating compound,such as a lacquer comprising cellulose, over the rubber insulation in acontinuous operation, using the heat imparted to the conductor by thevulcanizing step to drive off solvents and suitably cure the coatingmaterial. This has not proven economically practical for pricecompetition with plastic insulated conductors, because the vulcanizingstep,

or a partial vulcanizing step, heats the conductor throughout to a hightemperature in the order of 350 to 400 F. and the residual heat issufficient to render the rubber insulation too hot to receive thecoating even if the rubber insulated conductor is run through longtroughs of cold water between the vulcanizing and coating steps. The

'core cools more slowly than the insulation and in order by the meansemployed, thus creating the same situation as when insulating andcoating have been attempted in a single continuous operation. f

I have overcome these difficulties by performingrthe coating step on aninsulated conductor which is at room temperature, and heating onlythesurface of the insulation and not the ,core, using means and coatingcomposi tion both novel in this art. I

The structure of my applicator pots also enables the coating materialtherein to be well mixed and to maintain even viscosity during a coatingoperation and prevents it from scaling over. Inorder to obtain agoodbond between the insulation jacket and one or more coatings appliedthereon in accordance with this invention, it is important to soften theouter surface of the insulation but the insulation covering on thesethin conductors is so thin that substantial heating over an extendedperiod, such for example as that ."to 'which the core is subjectedduring vulcanizing, maysoften the insulation too much and will causesubstantial heating of the thinly insulated wires of the conductors andmay permanently damage the cord by deformation and stressing of boththethin insulation and the frail tinsel con- .a common jacket, andtelephone cord which asstated I above, is usuallya multicondu'ctor cord,comprising three or four conductors eachcomprising a conductive core ofIn fact for manufacturing colored several small gauge tinsel wiresindividually insulated and twisted together with all of the conductorsenclosed in a tight fitting insulating jacket, thus forming anon-circular core having larger and smaller diameters and a crosssectional shape which is very broadly similar to a three leaf or a fourleaf clover depending on the number of conductors. V

In some jacketed cords comprising two, three or four conductors theconductors are intentionally twisted together at a fairly short lay tomake the cords flexible. In other cords the conductors are usuallytwisted at irregular intervals, either because of the difference in feedtension during manufacture or carelessness of operators which permitstwisting during the course of a reeling-up operation. When coatingcompound has been applied to the surface of such a cord and the cord ispassed through rigid fixed wiping means of the prior art for the purpose7 of leveling the coating and imparting an even coating of the thicknessdesired for the final product, coating is removed from the high portionsor ridges of the structure where it is out of alignment with the orificeof fixed wiping means, causing the coating to be unevenly applied withlittle or no coating on the ridges and too much in the valleys androtation of the cord within the wiper orifice and relative to the wiperwill cause speedy wear of the wiper and undesired enlargement of theorifice therein.

Furthermore wipers of the prior art have been made of materials not ableto withstand the corrosive action of solvents of the kind presented inthe coating material which I prefer to use.

This invention overcomes this difficulty by providing a wiper, which isrotatable and slightly yielding and yet highly resistant to wear and theaction of solvents. Provision of a wiper which is slightly yieldableenables the orifice in the wiper to expand and defo'rm as required topass and satisfactorily coat a cord of non-circular cross section.Provision of a wiper which is rotatable as well as yieldable greatlyreduces friction between the cord and the wiper as the latter is able torotate with twists in the cord and is thus self-adapting to ridges andvalleys o'r twists in the cord.

An object of my invention is to provide an improved process for thecontinuous coating of insulated conductors and the like and for colorcoating such objects which are non-circular in cross section.

Another object of my invention is to provide a coated conductor or thelike comprising an improved coating.

Another object of my invention is to provide a novel combination orsystem of apparatus for the continuous coating of insulated conductorsand the like.

Another object of my invention is to provide improved apparatus forcarrying out individual steps of my process.

Another object of my invention is to overcome the deficiencies of theprior art and provide improved method and means for extruding coating oncords and particularly electrical conductors or cords of non-circularcross section including novel wiper and wiper nozzle means.

Another object of my invention is to provide improved apparatus forcoating such co'res, insulated conductors and cords.

Another object of my invention is to provide an applicator pot ofimproved structure and composition.

The invention will best be understood if read in connectio'n with thedrawings in which,

Figures 1 and It: show in side elevation at number of apparatuscomponents for carrying out the process, disposed in sequence along thepath of a traveling cord.

Fig. 1b is a cross-section of the applicator for antistick solution,taken along the line 1b--1b of Fig. 1a.

Figure 2 is a perspective view of an insulated conductor with itscovering partly cut away to show a plurality of coatings applied overthe insulation.

Figure 3 is a side view mo'stly in vertical cross section of apparatusfor extruding a coating on a traveling co'rd.

Figure 4 is a plan view of.the applicator portion of the apparatus shownin Figure 3.

Figure 5 is a view taken on the line 5-5 of Figure 3 but showing theorifice deformed.

Figure 6 is a side elevation, partly in perspective of the preferredmeans for fiash heating the traveling cord, and

Figure 7 is a wiring diagram showing the electrical circuit by whichautomatic control is achieved for turning on the gas jets of the flashheating means shown in Figure 6, and lighting them when the cord ismoving, and turning off the gas jets and applying cooling air to theportion of the cord within the flash heater when travel of the cord isstopped and simultaneously controlling other elements of the productionline.

The drawings show a production line comprising in longitudinalalignment, a letofl reel 10, the flash heating unit 12, the coatingcompound applicators 14 and 16, second or booster heating means 18a and18b, a wax applicator 2i), the cooling unit 22, an anti-stick applicator24, and a driven takeup reel 26.

Insulated cord C, which has been previously insulated with rubber, isdrawn from reel 10 and advanced successively to the above mentionedunits comprising the production line. Since the cord was insulated in aseparate, previous operation, both the insulation covering and theconductive core or cores are at room temperature or substantially atroom temperature upon leaving the letofi reel 10, and are at suchtemperature upon entering the flash heating unit 12. The flash heater isadjusted to cause the surface of the cord, when it issues from saidflash heater, to have a temperature approximating the maximumtemperature of the preferred temper ature range. Any given point alongthe insulated cord, when moving, remains within the heating means for soshort a period of time that there is little or no increase in thetemperature of the core by the time the insulated cord leaves theheating unit. The surface of the in sulation however has been heated toa temperature within the range of substantially ZOO-260 F. andpreferably within a range having about 240 F. as its minimum and about250 F. as its maximum. As the insulated cord passes through the coatingapplicators 14 and 16, successive thin coatings 11a and 11b (Figure 2)of the coating compound are extruded on to the surface of the rubberinsulation by means of specially moulded, yielding and long wearingwipers. With the first applicator 14 spaced approximately from two tothree feet from the flash heater means 12 and a second applicator 16spaced approximately two and one half feet from the first applicator,the surface heat of the rubber insulation is retained substantiallywithin said preferred temperature range while passing through saidco'ating applicators and is sufficient to effect slight expansion anddesirable porosity of the outer jacket and to initiate both good bondingand evaporation of the solvents from the successive layers of coatingmaterial causing them to bo'nd tightly and securely to the surface ofthe rubber jacket. More exactly the first layer of coating material isdeposited directly on, and bonds tightly to, the rubber jacket, and if asecond layer of coating is used it is deposited over the first layer ofcoating material and bonds tightly to and around it.

Preferably each layer of coating material is not over one mil inthickness and desirably is about one-half mil in thickness. If a thickerapplication of coating is desired, one or more additional applicatorsmay be employed.

Beyond the coating applicator means I provide blowers 18a and 18b forblowing air, preferably heated air, along the now-coated cord to driveoff remaining solvents and substantially dry and set the coatings uponthe insulation.

T temperature imparted to the cord surface by the speedy-1s means 18-shouldpreferably be substantially lessthan the temperature impartedwithin the flash heater 1-2. When coating rubber insulation of aninsulated conductortraveb ingat the rate of 100 to 300 feet per minutedepending upon the peripheral circumference, and with the flash heatingmeans imparting to the surface of the insulation a surface temperatureof from 240-250 F. as' it issues from the flash heater, and applying twocoating layers, each of approximately /2 mil in thickness, of a coatingcomposition comprising chlorosulfonated polyethylene, I have found thatair at a temperature within the range 160-180 F. applied to the coatedsurface over a distance of approximately 8 to feet accomplishes dryingof thecoating without transferring to the insulation-sufficient heat torender the surface tacky or to heat the conductive core or cores thereinsufliciently to impart residual heat which will injure the core or coresor; in any way impair the rapid curing of the coating.

As a precaution, and to overcome any residual tackiness which mightcause turns of the coated conductor to adhere together when reeled up onthe takeup reel 26, or piled up in cut lengths, I may apply over thefinal coating a very thin deposit of wax, which desirably can beparaflin wax, and then pass the conductor through a cooling trough ofrunning water, which may be of standard kind and of substantial length,for example on the order of six feet in length, or I may apply a coatingof suitable anti-stick solution such for example as a known cellulosecompound, in lieu of the wax before reeling up .the completed conductoron the takeup reel 26. his important that the deposit of either wax orcellulose compound be of only filmlike thickness, since a thicker layerhas a tendency to pick up dust and dirt. In; the case of certainconductors as for example conductors the insulation of which has beenonly partially vulcanized, it may be desirable before the finalvulcanizing step, and particularly when the conductor has been reeled upbefore the short final vulcanizing step and is placed in the vulcanizeron a reel, to apply either over the'thin wax or cellulose compounddeposit. or, if they are not employed, directly over the coating, a thinapplication of fine screen soapstone or talc as added protection inpreventing contacting turns from sticking together during finalvulcanization.

I find that a deposit of wax, which is so thin that it is extremelydifficult to measure its thickness, can be applied by passing the coatedinsulated conductor through a mist of liquid wax whichi provide withinthe wax applicator by means which will be described.

As best illustrated in Figures 1 and 3 the flash heating means 12comprises a unit which is from 6 to 9' in length, and has therein ateach side of the path of the insulated conductor, a number of jets 28for directing air, alone or mixed with heating gas, against and aroundthe surface of a portion of insulated conductor which is within saidflash heating means 12. A more detailed description is given below ofthe flash heating means illustrated in Figure 6.

Each of the applicator pots comprises a receptacle 39 which may be ofany suitable material, such for example as stainless steel or aluminum,to which the desired coating material is supplied from a supplyreservoir 32.

From the supply reservoirs 32 the coating material is fed into theapplicator pots through moulded flexible feed tubes 34 preferably ofpolysulphide elastomer, such as is commercially available under thetrademark Thiokol, which is practically impervious to coating solvents.Tubes 34 are controlled by the flow control valves 38. The particularflow control valves illustrated in the drawing are of the squeeze type.Each coating "applicator comprises a tubular entrance portion '40 onwhich is screwed a bushing 42 having at its rear extremityv an annulardisk 44,, the central opening of'which is preferab'ly' formed'by.a'copper eyelet 46' theorifice of: which is ofa diameter adapted to passthe insulated conduc tor without permitting: escape of coating materialfrom the applicator. Member 44 and its central copper eyelet thenarrowness of the container portion 30 in relation to the cord,conductor or other core traveling through it, taken together with theincreased height of the front end of the container. Prior artapplicators have been of greater width, usually three to four inches,and often circular, and are unsatisfactory because the rather largevolume of compound contained therein is not thoroughly mixed andagitated by movement of the conductor traveling through it and the uppersurface of the compound tends to thicken and form a crust; 7 I

The container portion 30 of the applicator pot -disclosed herein issufiiciently narrow so that the conductor of other core travelingthrough it, setsthe whole body of compound therein into a rotary motionand the increased height of the front end portion of the containerpermits the rising of the level of the compound within the front portionof the container due to this whirling or rotary agitation of thecompound, without spilling over. The travel of the core through thisapplicator pot keeps the compound therein well mixed and of evenviscosity and prevents it fromscaling over.

The rolling action of the compound obtained in my narrow container notonly keeps the components of the compound well blended but works out ofthe compound small air bubbles which may have become entrapped in it,due for example to airbeing drawn into the feed line or entrapped byeven slightly blocked air vents in the supply reservoir 32* from whichthe compound is fed.

In order to feed the coating material evenly the lower end of eachflexible feed tube 34 enters its applicator pot near its rear end, as'illustrated in Fig. 3, ata nonturbulent point behind the turbulencewhich is set .up near the elevated front end ofthe purposely narrowapplicator by the action of the insulated conductor passing through thisapplicator at speeds within ranges set forth herein.

Assembled at the discharge end of the coating applicator is a threadedflange on which is screwed a bushing 52 having a threaded outside faceto permit ready assembly of the wipe holder 54' and floating wipsy56.Holder 54 is a nozzle-like member supported only from its rear end, andfor ordinary size conductors may be tapered from an internal diameter ofabout to one of about /1". At its discharge end holder 54 is partlyclosed by the end flange 58 which serves as a stop for the floatingannular disk 56 which is the wiper means by which the thickness of thecoating'applied is determined. The diameter of the opening in end'fiange 58 is greater than the inside diameter of disk 56 but less thanthe outside diameter of disk 56. In assembling the parts the disk 56' isplaced in the nozzle-like holder 54 before the holder is secured onbushing 52; at the start-of operation the insulated conductor or othercore to'be coated is threaded through the orifice in disk 56 and thedisk is heldloosely against the endflange 58 by the viscous coatingcomposition and the movement of the cord. For applying a /2 mil coatingon an insulated conductor of .210" in outside diameter for example, Ihave employed with very good results a wiper'disk-about .100"

in thickness with an orifice of from .212 to .213" in diameter. v i i Imake both the wiper disk 56 and'the holder 54 of 3 material which isslightly flexible and yielding, so that the orifice in the wiperdisk54can enlarge anddeform to pass enlarged and twisted portions of a.cord,- and-so. that theholder 54 em bend and it's orifice inend flange 58'be nioved to;conform to bends-or unevenness in afoqrd passingthroughit. I also-prefer to make the feed; tubes somewhat-flexible forconvenience in cleaningithem.

I have found, that parts molded of polysulphide elastomer, such as iscommercially available under the trademark Thiokol, are both tough andyielding and are remarkably impervious to solvents and in particular tothe solvents employed in a coating composition comprisingchlorosulphonated polyethylene which I prefer to employ for coatingtelephone cord. I have obtained very excellent results with the parts34, S4, 58 and 56 molded of polysulphide elastomer type 500-A, type PR-lto which has been added ethylene diochloride to produce a formalreaction with sodium polysulphite of rank 2.0 cross linked through theuse of trichloropane, which is the compound commercially available underthe trademark Thiokol. Because of the resistance of this material tosolvents, its inherent toughness and its ability to bend and to bedeformed, the parts mentioned above have unusual life when made of it inaddition to having the very important advantage which results from theunusual combination of toughness and deformability and great resistanceto frictional wear by the cord being coated.

I have been able to compare the life of yielding wipes, of from 55 to 60durometer hardness molded from a polysulphide elastomer, with rigidwipes molded from Butyl rubber, neoprene and the like and have foundthat the former give far longer wear than the latter and better and moreaccurate wiping.

Since disk 56 is of lesser diameter than the holder 54 it is free tomove radially within the nozzle-like holder and since it is of yieldingmaterial and its orifice is able to adapt its size and shape to conformto a cord passing through it, it is able to compensate both for movementof the cord within the holder and the small irregularities anddifferences in diameter characteristic of the insulated cords beingcoated. Furthermore, floating disk 56 is arranged to rotate freelywithin holder 54 and thus when its orifice is deformed to conform forexample, to the shape of a cord of slightly ribbed non-circular crosssection, it will rotate with twists in the cord thus avoiding thefrictional wear to which a fixed rigid wire is subject.

In Figure I have illustrated in an exaggerated manner an annular wipe 56with its circular orifice deformed to pass a telephone cord having fourridges corresponding to four conductors enclosed in a common insulatingjacket. This wipe tends to rotate with twists in the cord and is thussubject to much less friction and does a far better job than if it wererigid and unyielding.

The apparatus I have described herein makes it possible to extrudecontinuous coatings on cords of noncircular cross section includingtelephone cord, and P O cord, in an economical and satisfactory mannerand without the unevenness of coating and the excessive wearing out ofwipers which have characterized prior art attempts to coat such cords.

As shown herein the coating applicators 14 and 16 are each supported onhubs 17 which are screwed into a clamp 60 adjustable along thehorizontal support bar 62 extending between the upright supports 64 and66 which between their upper ends also serve to support the ven tilatinghood 68 which is vented by connection with the vent pipe 70 extendingvertically from it. This serves to collect the solvents drawn out fromthe coating layers by the surface heat of the insulated conductor and todispose of them through said vent pipes.

Two heated air blower units 18a and 18b are shown positioned directlyafter the coating extruders. Each comprises a horizontally extendingheater tube portion 71 which is shown at floor level, a verticallyextending pipe 72 interconnecting the heated portion 71 with thehorizontally extending tubular portion 73 through which travels theinsulated and now coated conductor. Air, such for example as shop air,by which is meant air under pressure of substantially 100 pounds persquare inch such as is piped around many factories, is supplied intoheater member 71 intermediate its ends as for example by the tap t. Thisair is heated within tube 71 as by electrical heating units it providedwithin member 71 and connected by leads 132 and 134 to a 220 voltcircuit. A fitting 75 is screwed tightly into the rear end of tubularmember 73 and has a central bore to provide a passage for the insulatedand coated cord into the rear end of tubular portion 73. Air suppliedunder pressure to heater portion 71 goes upwardly through pipe 72 intoan air space surrounding the cone shaped center portion of member 75 andis thus discharged into the rear end of tubular member 73 around thecoated cord and in the direction of travel of the coated conductor, andserves to dry said coating and release accumulated solvents at the openend of the tubular member.

The size of the pipes 71, 72 and 73, the pressure under which air issupplied into this heater device and the extent to which it is heatedmay of course vary according to the nature of the operation. I haveobtained very good results with a device in which portion 71 is a 2 /2"pipe from 48" to 50" long and has assembled in its ends respectively two4,000 watt heaters approximately 15" in length to provide temperatureson the order of 200 F.

The temperature of the air issuing from the blowers 18a and 18b may bevaried within a temperature range of say 150180 F. by adjustment ofvalves v which control the pressure of the air as it issues from heatingunits 71.

The means for causing a deposit of wax on the coated insulated conductorfrom a mist of liquid wax comprises a closed receptacle 20 havingheated, fluid wax therein up to a level which is preferably maintainedat such an elevation that substantial space is left above it in saidreceptacle through which the insulated conductor is passed and wherein amist of the liquid wax is provided by means of one or more submergedpumps P driven by a motor M. The pump P has an inlet 74 for liquid waxbelow the liquid level within the wax container, and is connected to oneor more nozzles 76 by one or more tubes 78 for directing a spray ofliquid wax against a curved cone-like abutment member 80 and therebycreating a mist of liquid wax above the said liquid level. Asillustrated herein, member 80 is a carefully designed, semi-cone-shapedmetal member disposed at the conductors entrance into receptacle 20which is apertured to pass the traveling coated cord and serves todirect a cone of wax spray over and around the cord in the form of analmost invisible film. Ports 80 and 82 are provided in the side walls ofreceptacle 22 through which the traveling insulated and coated conductoris passed.

Upon leaving the waxer 20 the insulated, coated and waxed cord passesthrough the trough 22 to the takeup reel 26. A stream of cooling wateris continuously supplied to trough 22 through conduit 84 and exhaustedthrough conduit 86. Trough 22 is long enough to cool the conductorthroughout to room temperature and to harden the wax deposit.

Under certain circumstances, depending upon the materials with which acord is insulated and coated, instead of applying wax to the coated cordI prefer to pass it directly from the air blower means 18 to trough 22and, after the coating has been cooled and hardened in trough 22 butbefore reeling it up, to wet the cord surface with an anti-sticksolution. Such solutions and means for applying them are known and itwill suffice to say that such a solution, preferably of the cellulosetype, may be dripped from container 23 onto the absorbtive, flexiblesheets 24a and 24b, desirably of sponge or sponge like materialsuperimposed Within the receptacle 25, the cord being passed betweensaid sheets and wetted all around by contact with said sheets.

The flash heating means comprises the two outlet manifolds 28a and 28beach having a multiplicity of orifices 29. Air at room temperature issupplied to manisuitable coupling connections;

t? folds-28:11am 285 respectively through thetubes; 86aiand 8615, the.outer ends of: which are interconnected, as. shown iniF ig. 6, by anintermediate curved tube 86c.

Air from a suitable pressure controlled source, such as:shop' air issupplied under predetermined pressure to tube 86c through tube 88,valves 87a and 87b and the pressure indicators 89a and 8% respectively.I.have had good results using air issuing from conduits 86a. and 86bunder five' pound pressure.

Under normal operation these valves will be continu-' ously open so thatwhenever motor 92 is actuated air will be suppliedfrom compressor 90through conduit 88 into conduiti86c and then in opposite directionstothe burners 29a and 29b through conduit portions 86a and 86brespectively.

Asv shown herein conduits 86a, 86b and 86c are supported: by thestandard 94, having thebase 95, preferably telescopic so that its heightmay be adjusted, and by the standard branch arms 96a and 96b which areconnected totstandard 94 as by the T-connector 98 andto the coridllltiportions 86a and 86b by the T connectors or conplings100. and 102respectively. A valve 104 is shown n the air supply conduit 88 betweencompressor 90 and iltggunction with conduit portion 860 as by thecoupling Also connected to the tubes 86a and 86b is a gas supply tube108 from which branches 109a and communicafe with said tubes 86a and 86brespectively through The branch gas supply tubes. 109a and 109.: arecontrolled by solenoid valves 110a and 110;; respectively, positionedintermediate their ends, said branches 109a and 10% opening from saidgassupply tube 108 beyond the gas supply governor 112 connectedintermediate the ends of said gas supply tube 103; The'solenoidscomprising said solenoid valves are connected in an electricallycontrolled circuit such as is shown. in Fig. 7 and whenever said circuitis opened, at

any one of the switches comprised in the circuit, the

solenoid portions of said'members 110a and 11% actuate the valveportions thereof to instantly close said branch supply tubes 109a and1091: respectively, and conversely when the control circuit is closedthe solenoid portions of said members 110a and 11% of said branch armsrespectively cause thevalve portions thereof to open thus instantlyopening the gas supply circuitiand causing gasto be supplied from gassupply tube 109 through said tubes 109a and 109k and tubes 86a and 86brespectively to the said'manifolds 29a and 2%, from the orifices-29 ofwhich the gas is ejected by the pressure of the gas itself, supplementedby the pressure of the air continually suppliedto said manifolds,against, or in close proximity to, the surface of the insulatedconductor being coated;

more spark plugs 114, the point or points of which are bent down closeto the metallic surface of the manifold 28b", and these spark plugs arealso connected to an. electrically controlled circuit in such a mannerthat the spark plugs are actuated when gas is issuing in jetsfrornorifices 29 thereby causing a multiplicity of jets to be ignitedwhenever. gas is flowing to said manifolds 28a and 28b, said jets beingimmediately extinguished when only. air isbeing supplied to saidmanifolds 28a and 2815. It will be understood that, both while heatinggas is being supplied to said manifolds and while heating gas flow tosaid manifold is cut off, compressed air at room temperature will becontinually supplied to said manifolds and directed against the cordthrough the orifices 29. Aceordingly, if the. travel of the. cord isstopped for any reason, the flash. heatingzone and the portion of thecord therein will'be instantly cooled by air at room temper-attireis'sui-ng-alonefrom theeorificesi29, the'fs'uppl'y of gas having beencut otf by the operation of solenoid switch through which-electric poweris supplied from any: suitable power source (not shown) to as many ofthe=pieces of. apparatus comprising the production line as.- it isdesired by control simultaneously. Thus, in the single line diagramcomprising Fig. 7, power from a main power source is supplied throughthe main switch 120 to lead 122 through the lead 124 having therein-thecon? trol switch 126. Lead 122 is also connected in parallel with themotor, indicated at 116, which, through any suitable means, drivestakeup reel 26 thereby controlling the-travel: of the cord C; and withthe solenoid valves 110a and- 11% respectively, through branch leads 126and 128 respectively; and to spark plug means 114 throughleador. leads130 also branching from lead 122.

Thus,: the solenoid valves 110a and 110k will be instantly opened tosupply gas to the manifolds and jet orifices of the flash heater and thespark plugs will be sparking to ignite gas issuing from said orificeswhenever the conductor is traveling, and the supply of gas to saidmanifolds will be instantly cut off, and said spark plug means willbedeactuatedywhen travel of the conductor isstopped for any reason.

Otherelements of the apparatus comprised in the production linevillustrated in Figs. 1 and 7' may similarly be connected to lead 122 foractuation and deactuation simultaneously with said takeup reel 26, thesolenoid valves 110a and 110!) and the spark plug means 114. Asillustrated herein, the heaters in tubes 71 of blowers 18a and 18bareconnected to said lead 122 by branch leads-.132 and 134, respectivelyand the motor of the waxer 22 is shown connected to lead 122 by branchlead'136. a

If desired, other control switches similar to 126 may besuppliedwhereconvenient in the control circuit and such switches areshown in Fig. 7 included in the branch circuits 132, 134 and 136.

While I do not wish to be limited only thereto, I have discovered thatvery excellent results are obtained by using, and I prefer to use, acoating composition com.- prising a chlorosulfonated polyethylene whichis commercially available, with or without color as desired, under thetrademarks Hypalon tnd Hypalon 20.

I have had very good results applying a chlorosulpho nated polyethylenecoating in either two or three thin layers, each of less than one milthickness, upon a rubber insulated conductor traveling at a speed offrom 100 to 300 feet. per minute, the surface of which has beeninitially. and almostinstantaneously flash heated to a temperature in.the range of 240-250 F. by passing it through a short heating unitwithin which it is exposed to -a temperature suflicient to flash heatthe cord surface to=a temperature within said range. The resultingcoating' obtained iswear resistant and if pigmented is color fastiandfree from staining.

I have found that neoprene and other similar coating 7 materials tend todiscolor pigments and especially the brighter colors. Neoprene and likecoating materials may be used when a' black coating is desired or whenstaining of other objects by the coated insulated conductor is notimportant, and maybe very readily and successfully applied by myprocess. a

The extrusion coating processeswhich have been attempted onpartlyvulcanized telephone cord have ruined the cordfor coiling by.completing its vulcanization before it. has been set in the desiredcoiled. form. My processtmakes it possible to coat partly vulcanizedcords without heating them to a. temperature which will increase theirvulcanization, thusleaving them in. condition tobfe firstcoiled; andthereafter set in. a final vulcanizing step. lwhave: found that with themeansdisclo'sed. hereinfor initial flash heating the surface of aninsulated conductor, and with the conductor being advanced at a speed onthe order of from 100 to 300 feet per minute, a very short heating uniton the order of eight inches or less is desirable and a longer heatingunit may be too long and impair the process by imparting a substantialamount of heat to the core of the insulated conductor. I prefer to use aheating unit which is approximately six to nine inches in length and,while the insulated conductor is advancing at approximately the saidspeed of 100 to 300 feet per minute, create a temperature within theheating zone sufiicient to heat the surface of the insulation to atemperature substantially within the range of 200-250 F. as it leavesthe heating zone. With an insulated conductor of average size travelingthrough this flash heating unit at a speed within the range of speedsmentioned above a temperature on the order of 2000" F. within said flashheating unit will suffice to satisfactorily heat the surface of theconductor without heating the core sufficiently to damage it or preventthe satisfactory setting of the coating or coatings.

I have had very satisfactory results in coating rubber elements, such asa rubber insulated conductor, within my preferred coating compositionusing a production line along which the first coating applicator isspaced 24" to 30" from the flash heater; with substantially two to twoand one half feet between the first and second coating applicators; andabout three feet between the second and third coating applicators if athird applicator is employed.

If hot air reheater-blower means 18a is employed, the spacing of suchmeans from the last applicator is not at all critical and will bedetermined in part by the space available. I have obtained good resultswith such means positioned approximately two feet beyond the lastcoating applicator.

There has thus beendisclosed a process and resulting product andapparatus elements and combination of apparatus elements by which theabove stated objects are realized in a thoroughly practical manner.

What I claim is: v

1. In the process of coating a previously insulated conductor which isat room temperature the preliminary step of heating the surface of theconductor insulation to a temperature which is high enough to evaporatethe solvent from a layer of coating material applied on the heatedsurface of the insulated conductor, the length of time the insulatedconductor is subjected to heat and the heat employed being such as toheat only the surface of the insulated conductor without substantiallyheating the conductor core.

2. The process of coating an insulated conductor which comprises thesuccessive steps of heating the surface of a previously insulatedconductor, the temperature of which is initially at room temperature, toa temperature within the range of approximately 200 F.260 F. and

immediately passing the insulated conductor through a bath of coatingmaterial which includes a portion of solvent, and wiping the coatingmaterial to limit its depth to the desired thickness, the length of timethe insulated conductor is subjected to heat and the heat employed beingsuch as to heat only the surface of the insulated conductor to withinthe range specified above without substantially heating the conductorcore.

3. The process of coating an insulated conductor which comprises thesuccessive steps of heating the surface of a previously insulatedconductor, the temperature of which is initially at room temperature, toa temperature within the range of approximately 200 F.-260 F. andimmediately passing the insulated conductor through a bath of organiccombustible coating material which includes a portion of solvent, andwiping the coating material to limit its depth to the desired thickness,the length of time the insulated conductor is subjected to heat and theheat employed being such as to heat only the surface of the insulatedconductor to within the range specified above without substantiallyheating the conductor core.

4. The process of coating an insulated conductor, the insulation ofwhich is selected from the group consisting of natural rubber andsynthetic rubber, which comprises, heating the surface of the insulationto a temperature within the range of substantially 200 F.-260 F. withoutsubstantially heating the conductor core by exposing the surface of theconductor to a temperature of approximately 2000 F. along a distance offrom 6 to 9 inches while moving the conductor at a speed of from feet to300 feet per minute, and passing the portion of the conductor thesurface of which has l'een so heated successively through a first bathof chlorosulfonated polyethylene and through a wiper having an orificeof a diameter such that the resultirg coating is approximately one halfmil in thickness, and through a second bath of chlorosulfonatedpolyethylene and wiping the second coating thus obtained to limit thedepth of the second coating also approximately to one-half mil inthickness, and passing the insulated conductor which is now coated witha plurality of coatings through a cooling medium to set the layers ofcoating composition.

5. Apparatus for applying coating on an insulated conductor whichcomprises, a let-off reel, a take-up reel, and means for driving thetake-up reel, an air and gas manifold disposed along the path of theinsulated conductor in travelling from the let-01f reel to the take-upreel, said manifold comprising a multiplicity of jets directed at thepath of the insulated conductor, air and gas conduits connected to saidmanifold, and means for supplying gas and air to the manifold throughsaid conduits including valve means for the gas conduit, means forigniting gas supplied to the jets of said manifold, and means responsiveto the movement of the conductor for controlling said gas supply meansand said gas igniting means, a container for a body of coating materialhaving inlet and outlet orifices through the insulated conductor is led,wiper means for controlling the depth of the coating deposited on theinsulated conductor, and cooling means for setting the coating.

6. The apparatus claimed in claim 5 in which the gas igniting meanscomprises, spark plug means positioned adjacent said manifold, solenoidmeans for controlling said valve means, and electric control circuitmeans .in which the spark plug means and the solenoid means areconnected, said control circuit means including switch means responsiveto movement of the conductor.

References Cited in the file of this patent UNITED STATES PATENTS1,033,912 Lendi July 30, 1912 1,817,122 Black Aug. 4, 1931 1,956,401Russ Apr. 24, 1934 2,072,557 Hinsky Mar. 2, 1937 2,175,099 Abbott Oct.3, 1939 2,288,129 Feldhausen et a1 June 30, 1942 2,382,275 Van Lin et alAug. 14, 1945 2,421,652 Robinson et a1. June .3, 1947 2,448,799 Happoldtet al Sept. 7, 1948 2,539,147 Loucks et a1. Jan. 23, 1951 2,600,567 MolJune 17, 1952 2,642,035 McDermott June 16, 1953 2,668,700 Zimmerman Feb.9, 1954 2,684,050 Larsen et a1. July 20, 1954 2,734,478 Reynolds et a1Feb. 14, 1956 2,789,922 Allen Apr. 23, 1957 2,811,746 Lerch Nov. 5, 1957FOREIGN PATENTS 223,529 Great Britain Nov. 13, 1924

1.IN THE PROCESS OF COATING A PREVIOUSLY INSULATED CONDUCTOR WHICH IS ATROOM TEMPERATUER THE PRELIMINARY STEP OF HEATING THE SURFACE OF THECONDUCTOR INSULATION TO A TEMPERATURE WHICH IS HIGH ENOUGH TO EVAPORATETHE SOLVENT FROM A LAYER OF COATING MATERIAL APPLIED ON THE HEATEDSURFACE OF THE INSULATED CONDUCTOR, THE LENGTH OF TIME THE INSULATEDCONDUCTOR IS SUBJECT TO HEAT AND THE HEAT EMPLOYED BEING SUCH AS TO HEATONLY THE SURFACE OF THE INSULATED CONDUCTOR WITHOUT SUBSTANTIALLYHEATING THE CONDUCTOR CORE.